1. Field of the Invention
The present invention relates to a wire bonding apparatus and method, and more particularly, to a heating apparatus and method for devices, such as semiconductor devices.
2. Prior Art
Generally, the substrates of semiconductor devices are made of a metal. Recently, from the standpoint of cost reduction, in such devices, numerous chips are mounted in a dense concentration on a resin-made substrate, and wire bonding is performed on these chips; and after which the chips are all molded at the same time, thus forming into individual devices.
In wire bonding, the undersurface of the substrate is heated by a heater block for the purpose of maintaining the surface temperature of the device at a high temperature. This heating is done in order to improve the reliability of bonding. However, resins have the softening temperature of as low as, for instance, approximately 150xc2x0 C. In addition, resins have high heat insulating properties. Accordingly, it is difficult to heat the surface of the chip, which is to be bonded, to a high temperature using a method that heats the undersurface of the resin-made substrate with a heater block.
A wire bonding apparatus equipped with a heater block for accomplishing the heating as described above is disclosed in, for instance, Japanese Patent Application Laid-Open (Kokai) No. H4-262545.
In view of the above difficulties, it is conceivable to accomplish heating by blowing a hot air draft onto the bonding parts of a chip from above. Japanese Patent Application Laid-Open (Kokai) No. S59-184537 discloses a method in which heating is accomplished by blowing a hot air draft onto the upper surface of the chip.
However, even in the hot air blowing method, there is a possibility that the substrate will soften if heat producing a temperature of 200xc2x0 C. is applied for a long period of time in order to perform stable bonding. If the substrate softens, the ultrasonic energy and load of a capillary will escape during bonding by being absorbed by the substrate, resulting in that stable bonding cannot be performed. Thus, such softening must be prevented.
Accordingly, the object of the present invention is to provide a wire bonding apparatus and method which performs wire bonding while maintaining the upper surface of a device at a required temperature and at the same time maintaining the device at a temperature that causes no softening or deformation of the resin substrate of the device.
The above object is accomplished by a unique structure of the present invention for a wire bonding apparatus in which a device that includes a resin substrate is placed on a heater block that has a heater, held by a frame retainer and subjected to wire bonding; and in the present invention, the temperature of the bonding surface of the device is maintained at a temperature that allows bonding, while the heater block is cooled by a cooling means so that the temperature of the heater block is maintained at a low temperature that does not soften the resin substrate.
The above object is accomplished by another unique structure of the present invention for a wire bonding apparatus in which a device that includes a resin substrate is placed on a heater block that has a heater, held by a frame retainer and subjected to wire bonding; and in the present invention, the apparatus is provided with a chip heating means which is disposed above the heater block so as to heat the chip portions of the device, and a heater block cooling means which is installed in the heater block so as to cool the heater block; so that the temperature of the bonding surface of the device is maintained at a temperature that allows bonding, while the heater block is cooled by a cooling means so that the temperature of the heater block is maintained at a low temperature that does not soften the resin substrate.
The above object is further accomplished by a unique wire bonding method of the present that is executed in a wire bonding apparatus in which a device that includes a resin substrate is placed on a heater block that has a heater, held by a frame retainer and subjected to wire bonding; and in the method of present invention, the temperature of the bonding surface of the device is maintained at a temperature that allows bonding, while the heater block is cooled by a cooling means so that the temperature of the heater block is maintained at a low temperature that prevents the resin substrate from softening.